Problem: Solve for $p$ : $11 = p + 18$
Subtract $18$ from both sides: $ \begin{eqnarray} \\ \hphantom{11 {- 18}} &\hphantom{=}& \hphantom{p} \\ 11 &=& p + 18 \\ \\ {-18} && {-18} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 11 {- 18} &=& p \\ \end{eqnarray} $ Simplify. $ p = -7$